Tennessee, like all states, is facing increased demand on its transportation infrastructure. The Interstate 24 corridor, a 185 mile stretch from Kentucky to Georgia has been identified in the Tennessee Department of Transportation (TDOT) Long Range Transportation Plan (Plan GO) as critical to statewide mobility and regional connectivity. One critical segment of this corridor deemed high priority is the “Moccasin Bend” segment tucked in between the Tennessee River and a steep bluff in downtown Chattanooga.

TDOT needed a high accuracy 3D model of this complex area in order to evaluate many different multi-modal design alternatives. Continental Mapping brought a mobile lidar solution to the problem. Mobile lidar, when fused with aerial lidar and aerial imagery, creates a dataset that allows for complex, high accuracy design alternative development, and provides a cost-effective reusable 3D mapping dataset that can be used for years to come.

Challenges Faced:

Moccasin Bend along I-24 in Chattanooga is a crowded, constrained corridor. Just east of this location lies the heart of the city and connected to the south is an interchange with the equally-busy I-75 corridor. What makes this corridor particularly difficult for easing congestion is a different sort of crowding: hugging both sides of the corridor are natural and industrial obstacles.

This trans-loading facility with mapping superimposed helps get freight off of I-24. One challenge here is how to expand this capability in a tight corridor.


There is almost nowhere to expand

  • The Moccasin Bend of the Tennessee River parallels the north side
  • A major rail line and trans-loading facility hugs the south side (seen in above image)


I-24 is one of the most vital interstate corridors connecting Georgia and Illinois. Moccasin Bend has become a major choke point along I-24 due in part to increased traffic.

Public Outcry:

Chattanooga commuters are demanding a resolution. Some suggestions include:

  • A double-decker corridor around Moccasin Bend
  • A truck tunnel designed to funnel freight away from the bend
  • A pedestrian superhighway down the middle of the corridor


TDOT’s Plan GO concluded that continuing to add lanes would be impractical and financially unfeasible.

Challenges Met:

TDOT recognized the need for high accuracy, comprehensive 3D mapping of the entire corridor and surrounding area. High accuracy base mapping provides all interested parties with one version of the landscape giving designers 3D data that can support multiple design alternatives.

Continental Mapping proposed a hybrid data solution comprised of mobile lidar, aerial lidar, aerial imagery and field survey. Each mapping technology was used for its respective strengths: aerial lidar for accuracy and broad coverage, aerial imagery for planimetric mapping and orthophotos, mobile lidar for high accuracy data of roadways, and land survey to control all the data and collect supplemental data in obscured areas.

The diverse inputs were fused to derive one comprehensive 3D dataset.

A comprehensive 3D data set means:

— No second guessing the data

— Long term adaptable planning

— No returns to field

— Long term cost savings

— Timely design and planning

— 3D modeling to better shape perspective and improve efficiency

Final deliverables for the project included 1" = 50' planimetric mapping, 1-foot contours and a DTM. Hard surfaces were mapped to a 0.1' vertical accuracy.

Mobile lidar-derived point cloud showing part of a complex interchange

Continental Mapping

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Continental Mapping Consultants, Inc. is a leading small business provider of high-quality, innovative, and comprehensive geospatial services.

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